In the early part of this century room air chilling was unknown and heating was limited to direct radiant types from sources of burning matter, such as a stove or fireplace. Large facilities such as factories and apartment buildings were efficiently heated by steam or hot water systems. It was not until the development of the high efficiency heat exchanger that hot air systems came into widespread use driven by the great demand for air chilling equipment. Because air chilling requires air displacement, it has made economical sense to use air heating as well as chilling in a common system, i.e., a system which recycles the air within the enclosed environment. A significant advantage to the moving of air is that it can be constantly filtered thereby maintaining a clean air inventory. Air cleaning technology has brought the advantages of low dust count levels, low pollen levels, and is responsible for low airborne pathogen levels in living spaces as well.
British 1,302,878, Staunton, U.S. Pat. No. 3,568,416, and Wright et al., U.S. Pat. No. 4,512,891 all teach various framed or otherwise supported filter media units for use in air handling systems. Flat filter media elements at very low prices are provided to a mass market of hundreds of millions of units per year. Wegrnan, U.S. Pat. No. 3,306,069 teaches a front assembly for a room air conditioning unit including placement of filter media. Il Yoo, U.S. Pat. No. 4,978,375 shows an effective means for supporting a filter media during use without the need for an external frame or grid structure.
Mass usage of filter elements, has driven a need for simplified installation and replacement of these units. Frequently air handling units made of sheet metal and designed in the absolutely least expensive way tend to be poorly designed for ease of filter replacement. Filters, in such equipments are also held poorly so that air flow around the element is more likely. Koushiafes, U.S. Pat. No. 4,174,205 teaches an improved filter media unit having a replenishable supply of media. This, of course, could result in an improved heating efficiency through the improved maintenance of high air flow by more frequent change of filter media. Delany, U.S. Pat. No. 4,701,196 teaches a draw style filter unit to be inserted into a box which is made part of a fumace system structure. Soltis, U.S. Pat. No. 4,133,653 describes a residential type filter assembly including a housing, prefilter, collector, ionizer, and a unique mode of suspending an ionizing wire within the assembly. The latter is similar to the instant invention.
The prior art does not address directly the problem of providing a highly simplified filter installation coupled with assurance of a tight fitting installation in a inexpensive assembly. These three requirements tend to be mutually exclusive in the art and in the commercially available solutions today. The instant invention provides an elegant solution which is at once unique and yet highly practical in the commercial sense.